Vanagon digijet woes!!! HELP!

[greenacarina]

I am just about at the end of my rope on this one. I've got an 85 Vanagon, 100% rock stock. Starts up and runs fine cold, I can drive about 4 or 5 city blocks and it gradually loses power. As far as I can tell it's going way rich. It will get to the point (after 8 or 9 blocks) that it will barely move under it's own power...idles fine, revs fine with no load, can accelerate somewhat on the flat but will surge at about 2500 rpm (WOT). This problem is very consistent as I drive the same "test route" and the power drops off at the same points in the drive. So far I've tried 3 different ECU's, 2 coolant temp sensors, 3 airflow meters, changed the fuel filter, driven the route with a pressure gauge (fuel pressure remains constant), all the tune-up parts are fairly new and in good shape, the needle on my tach always stays very steady. To me it seems to be fuel and heat related and at this point I'm suspecting an injector or 2. Anyone want to chime in on this one? I'm very much open to ideas and opinions!!
Thanks!!
Chris

[raygreenwood]

QUIT SWAPPING PARTS AROUND DAMMIT! That is NOT how to troubleshoot. You may fix what really is just a bad connection...and never know it. The VOM values are in the book, a simple VOM test will tell you whats good and not good.
That being said....it sounds exactly like a feeder pump problem. Most digifant uses a feeder pump in the tank. If its going bad....or if the sock filter attached to it is clogged....this exact thing will happen. Having steady fuel pressure is NOT a good sign. You have a rising rate fuel pessure regulator yes/no? One with a vacuum line right? it should be low pressure at idle...like 32-34 psi and about 38-42 at WOT...or about mid range on. Have you checked that? Also, this will not be found at idle generally. The engine requires too low of a volume to outstrip the main pump at low rpm. When you speed up....most especially under load...the weak or clogged feeder pump can no longer keep up...and the main cavitates.

Also, a bad 02 sensor.,..if you have one....can cause similar symptoms. So can a bad knock sensor (mostly watercooled) as it keeps the advance way low. Also, do you have an idle air controller? If so...it could be sticking. My bet is on the feeder pump. Ray

[Guest]

Do you have the factory service manual? If not buy it. Ray's right. You need to test your components not guess. This is not voodoo. It sounds like you've done a tuneup. If you reset the timing did you disable the Idle air controller properly? learn how the parts work as a sytem and look at them at such?

[j-bro]

I don't think digijet has a feeder pump but this does sound like it could be a fuel supply issue. You mentioned pressure is constant but did'nt say what it was. Test your fuel output volume and your pressure regulator; and everything else.

[greenacarina]

OK...first I should clarify that I did check my wiring connections first (yes, I cleaned up all my grounds as well), tested my coolant temp sensor according to the manual (as this seemed the most likey suspect) and swapped out the ECU and airflow meter with known good "test" units...so I guess the long and short of it is I'm not just throwing parts at it hoping it fixes itself...really trying to take a logical approach. Digijet doesn't have a prepump and the main pump is brand new (from the previous owner). I was thinking it was a fuel volume issue as well which is why I drove around with the pressure gauge attached watching for pressure to drop off as the car failed. One of the obstacles I'm up against is the conditions that cause the failure...hot and under load. It's hard to test components with a VOM while I'm driving. :)

[raygreenwood]

Ok...thats sounds better. dorry..wasn't trying to be your mother . Just trying to impress the other flock of problems that you can run into.
Like I noted on a previous post on a different thread. I am am less in tune with what exact system equipment the busses had. Most of my digifant experience (and digjet...technicaly digifant 1) is watercooled. So...list what your system does have. You have an 02 sensor right? Do you have WOT switches on the throttle of any kind?.
I would check bery carefully for a feeder pump. many people have them and do not know it. That being said....if the main pump is getting weak, the filter is clogged, or the sock strainer is cloged.....will act like this. This is by the way...precisely why 90% of all later applications DO have a feeder pump. The l-jet and digifant style pumps had a real habit of losing prime and cavitating. Also...if you have any vacuum leaks at all....you can be having fuel pressure problems from the regulator. I doubt if you have a knock sensor. Its difficult with aircooled. Wait....you have coolant temp sensors? Then its watercooled?


You noted that you are sure it does not have a pre-pump. It would be inside the tank if you do.. A really quick way to tell if it IS a volume test...other than pulling the pump and testing volume...is to slave another spare pump in line in front of it and wire them together then drive.

So you drove with a gauge on? Other than the variation that should happen from the vacuum regulated fuel pressure...do you notice needle fluctuation when idling? If so....chances are...the pump is suspect.

...................WAIT...WAIT. Something was nagging me....does this problem happen mostly under load?....meaning that if you are barely cracking the throttle and maintaining speed...it seems to run okay.....but put some foot into it....and it bogs...and blows black smoke?

If that is it.....and it only happens when warmed up.....meaning the cooling fans may be active....and the idle air controller (ifyou have one) is closed......CHECK YOUR MAIN ENGINE BLOCK GROUNDS!! Digijet and more precisely...digifant suffer from poor grounding. A loose or corroded main ground anywhere on the block will cause this exact problem as well. It causes low voltage at the grounds for the injectors. Since it runs you lean...the 02 sensor is trying to compensate....and cannot. It fights itself. Ray

[wbx]

To me it seems to be fuel and heat related and at this point I'm suspecting an injector or 2. Anyone want to chime in on this one? I'm very much open to ideas and opinions!!
Thanks!!
Chris

First of all, i am not a FI expert, i just happen to own an '84 westy and have done a fair bit of work on it.

I agree that it sounds like a fuel and heat related issue. On digijet, the tempII sensor (coolant) is pretty instrumental in telling the ECU what sensors to listen to or ignore. Sounds like you've checked it, but double check . Secondly, it would probably be helpful if you knew that your engine was running either rich or lean at this time. An easy way to do this is simply checking the 02 output with a voltmeter after your engine has gotten hot and lost power. 1v is rich, 0v is lean (unfortunately, it doesn't tell you by how much). The signal should oscillate between the two very quickly. It must also be hot, though, since our 1-wire O2 sensors cool off at idle and no longer send a signal to the ECU (which then just switches to a default mode).
It seems as though a bad injector would cause consistently poor running - not just at temp.

What other symptoms are there?

Have you gone back to the basics and checked your timing, etc.? A clogged filter is also super easy to check (and would fit the symptoms, too).

And for Ray's edification:
All busses were watercooled from 1983.5 through 1991, used O2 sensors, and were a dumbed down version of L-jet. '83.5-85 (digijet) used a vacuum advance for spark (ecu had nothing to do with spark), and '86-'91 (digifant) got true electronic control over spark as well as fuel. There is no feeder pump in the gas tank, and the engine is in the back . There is also no knock sensor on any model.

[raygreenwood]

Thanks WBX...I will scribble those dates on my cheat cheets . Thats a pretty good description of digijet (digifant 1 basically).....a dumbed down L-jet. The thing I do not know about digijet....compared to digifant.....is wether the injectors canbe checked as weries resistance...meaning since the are bank fired, you generally can read one and get the resistance of thre whole series. Unplugging one at a time reveals which is off the most in resistance.

Its good you mention the 02 sensor again. On some vehicles....and I don't know this about L-jet or digifant....but its simple to check......if the 02 sensor is badly corroded and has lots of resistance...it can cause a poor starting problem....even though it should not be working until heated up. But, simply unplugging it and letting the system default to limp home mode may at least tell you if its functioning....as would a vom check aftee warm up, Ray

[wbx]

Thanks WBX...I will scribble those dates on my cheat cheets . Thats a pretty good description of digijet (digifant 1 basically).....a dumbed down L-jet. The thing I do not know about digijet....compared to digifant.....is wether the injectors canbe checked as weries resistance...meaning since the are bank fired, you generally can read one and get the resistance of thre whole series. Unplugging one at a time reveals which is off the most in resistance.

Looking at my wiring diagram, the injectors for digijet are in parallel. I believe this applies to all years of vanagon (regardless of digijet or digifant). This makes sense, too, just looking at the wiring harness in my van... I could be wrong on this one, though (but am pretty sure).

-Damon

[raygreenwood]

Yep...being that they are split from side to side instead of on one rail, they have two circuits even though they all fire at once...or is it one circuit and two access points. But...I believe the resistance reading is still in series per each pair...when read from the ECU end of the harness. I believe each side has a common injector ground point with both + wires coming to a common connector inside the ECU...though they use 4 wires. I think the basic L-jet diagram reads 43/2 and 43/3...or is it 1 and 2. Ray

[Danborn]

Connections connections? I had exactly the same problem, and it turned out to be the main ground connection, the wires was eaten up an inch, but you coulden see it, check also the ground between gearbox and body! Even a bad ground connection can show all is ok, but under load, the problem occurs. Be sure that all the wires are ok. The cable between the battery and starter could also be corroded. BTW it has no feeder pump

Jesper

[raygreenwood]

Well put. ANY bad grounds in any system, wether its the EFI system itself or charging and ignition systems, can cause these problems.

Yes...I understand that this particular system has no feeder pump. In my opinion, it probably needed one. Almost every system of similarity folowing it, has one and for good reason. But the fact that it does not use a feeder pump also means that the pump does not have to lose very much capability at all....even through age alone....before it has volume issues. Also, even if the pump was replaced just last year, if there was water in the system and it did not run for a while, the pump can very well be shot. All it takes is a few rust flecks in the right places. Ray

[j-bro]

You've just reminded me of a cross coutry trip when everytime I'd get up to speed the engine would bog down. My first thought was fuel pressure problem. After several stops trying to figure it out found the tach lead to the control unit had a bad connection at the coil. Fixed the connection and ran fine from Nevada to Montana and back to California.

[MrMike]

Chris

I have the exact same bus ( 1985) ( 1.9 wbx) and have been battling the exact same proplem for 3 years now, It comes and rarely goes. And that is the confusing part,
when it has ran well . I think I have ENJOYED this bus 5 days in total.
What a PIG!!

I too have changed everything from soup to nuts and have rewired the whole engine compartment. In addition spent in excess of 4k at VW and non-vw shops chasing this specific problem and another 6k for other repairs including heads, oil tubes, seals and clutch and all brake parts .
brake master and booster too.
O2 sensor, wiring, all grounds, ( even double straped the engine ),
relays, ecu, ignition switch, all sensors, idle stabilizer, whole distributor
( that was a VW guess-tamate ) pickup signal amp, coil , wires and plugs
(all Bosh ) Gee have I left anything off the list???? oh ya!! 2- fuel pumps.

So far the only thing I have not replaced are the 2 front doors, back window and rad fan. steering wheel, seats and horn.

I now know way more than I should have to about a Vanagon
Water-cooled bus. For some reason mine eats O2 sensors. I got about
12 k before the last one was done, and even then it only ran intermittently well.
When it does, it is great but I have no reason for why it ever does.
It may run good one trip then, stop for gas jump back in and it runs like crap. I shut it of wait 10 min and it may run fine. Some days the symptom
persists till the next day. Some days it runs like poop right from the get go.
Stop - shut it off - wait - restart - it runs ok. (????????)l

I've even done the Tatalum capacitor mod to the airflow box. Man, I really thought that did it 'cause it ran real good for 4 days, lots of power through
the whole band. Then boom, it went for a poop
This more severe problem seems to follow high ambient temps when it is from the start. Probably because the coolant is already warm ( 30+ degrees celcius days) @-10 to - 40 below I don't ever have this problem. I've used the Bentley temp/res charts for the temp1 and temp2 to
formulate and substitute fixed resistors for both of these sensors.
selecting different water/ air temp combinations
The problem stays, I can always have the system run (open-loop)
by disconnecting the temp2 sensor while the engine is sputtering
it does run better at idle ( at 2200 -2500 rpm ) but way too lean,
the first night I did this the manifolds got a little red. I don't recommend this as a test proceedure...
The only conclusion I can come to is: the bosh replacement single wire
sensors I've been buying are not within the original WBX specs.
and Bentley's $150 book isn't worth the paper it's printed on.
I've yet to talk to even one happy 84-85 gas WBXR owner.
The guru idiots whom can never say "I DON'T KNOW" call
this "VANAGON SYNDROM" - WHAT A LOAD OF HORSE poop
And the $168 plug -in ( op amp) for the airflow meter ????
Come-on ! Can anyone tell me about this first hand???? poop NO!!!
If any one has found this to be a solution, they certainly don't brag it up..

I curse the day I ever bought this Van. and personalyl, I think
Volkwagon should step up and offer a solution other than the ol'
Subaru / Jetta engine conversion. And at the very least, offer each
and every one of us
a rather lengthy apology.
So angry I could spit !!!!!
Mr Mike

[MrMike]

PS. I didn't say "POOP" appearently the" morality police" have change my nouns. I guess they have never been to a farm...........
or had a Vanagon,,,,,,